Dishwashing machine operation



y 1954 s. B. F. CARLSTEDT 2,684,921

D ISHWASHING MACHINE OPERATION Filed Oct. 18, 1949 2 Sheets-Sheet l y 1954 s. B. F. CARLSTEDT 2,684,921

DISHWASHING MACHINE OPERATION Filed Oct. 18, 1949 2 Sheets-Sheet 2 Patented July 27, 1954 DISHWASHI-NG MACHINE OPERATION Sven Biirje Fredrik Carlstedt, Malarhojden, Stockholm, Sweden Application October 18, 1949, Serial No. 121,940

Claims priority, application Sweden May 4, 11.949

1 Claim. 1

My invention relates to dish-washing machines of the type having an upper part for receiving articles to be washed, a lower part providing a trough communicating with said upper part, a conduit for supplying washing liquid to the interior of the machine, and a rotatable shaft in said lower part driven by an electric motor and carrying at 'least one impeller member to throw liquid upwardly from said lower part against the articles in said upper part.

In the operation of dish-washing machines of this type and similar machines it has earlier'been the rule that the washing machine from the Very beginning of the operation thereof or at least after a minimum interval from the starting of the impeller member should contain the maximum quantity of washing liquid. It was thus the general belief that the washing machine ought to operate ,in this way in order to obtain the best possible washing effect during the shortest time. My invention is based on the observation that the washing eiiect very surprisingly becomes considerably higher if the washing liquid is fed into the machine only relatively slowly, the machine thus during the major period of and even for the entire washing operation working with a smaller quantity or" liquid than the maximum quantity which the machine is capable of receiving.

One object of my invention deriving "from that observation is to provide a dish-washing machine into the interior of which washing liquid is supplied continuously when and so long as the impeller member is in operation. This co-ordination of the control means for the impeller member and means controlling the conduit for supplying washing liquid to the machine makes it possible both to simplify the construction as well as the operation of the machine. A further object of my invention is to provide means for retarding the supply of washing liquid to the machine in order to limit the consumption of hot Water toreasonable proportions. However, it constitutes only an advantage according to my invention to feed additional liquid into the machine after an overflow or like device for limiting the quantity of liquid in the =machine has become operative, because in that way the washing liquid in the-machine is prevented from becoming too dirty and additional heat is supplied to the same which thus will be kept at the temperature desired.

Further objects and advantages .of my invention'will be'apparent from the -following description of a preferred embodiment of the invention container.

considered in connection with the accompanying drawings which form part of this specification and of which:

Fig. .1 is a side-elevation of a dish-washing machine according to the invention;

Fig. 2 is a corresponding view, partly in verticajl'longitudinal section;

Fig. 3 is a sectional view, on an enlargedscale, of a valve unit constructed in accordance with the invention and arranged in the conduit for supplying washing liquid to the machine; and

Fig. 4 is a diagram.

Referring to the drawings, lil designates -a lower container or part of a washing machine,

said container or part having a shape resembling a trough and suitably being made of cast-iron with a relatively great wall thickness. In said part it is rotatably mounted a horizontally extending shaft -l2 carrying outside of the machine a pulley I l, a belt 28 passing about said pulley and a smaller pulley it .of a driving electric motor 58. The shaft l2 carries a small number of impeller members, in the illustrated embodiment three blades 22 disposed along the length of the shaft one beside the other but displaced in relation to one another round the circumference at angles of 126. Each blade 22 i statically balanced by a counter-balance 24. In the lower portion of the part Ii] is adrain .26 which is permanently open and extends in a tangential or substantially tangential direction backwards in relation to the direction indicated by the arrow '28 in Fig. 2 of the ciculation movement of the agitated liquid. The electric motor !8 is of the series type, i. e. the type thenumber of revolutions of which is reduced in accordance with the increase of the load.

Above and in open communication with the lower container or part It is located an upper container or part 39 for receiving the articles to be washedsaid part 139 suitably having walls made of thin sheetplateand being of considerably greater height and width than th lower The shaft l2 may be displaced somewhat in relation to the center line of the upper container 31), as willbe seen from Figs. 1 and 2, the ,wall of the'lower container opposite to said center line extending in a sloping direction towards the horizontal plane. The articlesto ;be washed, for example plates '32, are located the container 30 on'suitable stands or basketst l.

On one end Wall ofthe lower container It! is secureda valve box '36 shaped for this purpose with a flange '38 screwed onto the container. Another valve box 40 is connected to thevalve box 36 by means of screws 42, a packing 44 being interposed therebetween. A valve body 45 of preferably hexagonal cross-section is displaceably located within a bore 48 of cylindrical crosssection arranged in said valve box 40. Because of the hexagonal cross-section of the valve body 46 flow passages are formed between said valve body and the wall of the bore 48. By means of a spring 56 the valve body 46 normally is kept pressed against the packing 44. From said valve body extends a stem 52 which projects a short distance upwardly out of the box 36.

Above the stem 52 a switch 54 is tiltably mounted at a point 56 on the flange 38, said switch in a manner known per se encasing mercury which depending on the angular position of the switch closes or opens the circuit for the supply of current to the motor l8 through cables 58. The tiltable switch 54 is operated by a switch rod 60 which may extend upwardly to the upper part of the machine and there be provided with a button 62 or similar member and the lower end of which suitably enters an angular-shaped recess 64 of the switch. In the position shown in Figs. 1 and 2, the button 62 is pressed down, in which position it may be kept by any suitable means known per se, for example a ratchet device becoming operative on a quarter of a revolution. In this position the motor 13 is energized and the valve body 46 has left its valve seat, a free passage past the same thus being established.

Washing liquid preferably supplied from a hot water conduit enters the inlet valve through a connection 66 provided in the valve box 49. In the connecting passage 68 between said connection 66 and the bore 48 is a restriction which is entered by the conical point of a set screw 74 guided in the thread of a bore 16 provided in the valve box 49. Upon adjustment of the set screw for obtaining the desired degree of throttling the bore 16 is sealed by a screw 18.

The Washing liquid after having passed by the valve body 46 flows through a connection piece 80 in the valve box 36 and a conduit 82, and before entering the dish-washing machin proper preferably passes through a protective device 84 preventing back-flow. Said protective device 34 has an opening 86 communicating with the outer atmosphere so that in case a vacuum should be created in the hot water conduit, the liquid already contained in the machin is prevented from being sucked back into said conduit.

When the button 62 is pressed down, the motor I8 is started while at the same time the valve 46 is opened to supply washing liquid, in the first instance hot water, to the interior of the machine. The supply of liquid to the machine is then continued as long as the motor is in operation, said supply, however, because of the restricted flow passage in the valve box being of such reduced rate as to have the machine operating with less than its full quantity of liquid during the entire washing process or, if the dirt on the articles to be cleaned is of a harder consistency than normally, during a considerable period of said washing process. The full quantity of liquid is determined by the drain 26 substantially preventing escape of liquid until the level of the liquid in the container H] has reached a predetermined value, at which level the static liquid pressure directed downwardly overbalances the tangential component of motion imparted to the liquid by the blades 22, sufficiently to create an outflow of liquid through the drain at a rate equal to the rate of inflow. The washing operation being finished, the switch rod 60 is moved upwardly which causes the spring 50 to close the valve and the mercury switch to swing upwardly so as to cut off the current to the motor l8.

Because of the restricted supply of washing liquid to the machine the cleaning effect, as already mentioned above, is better than would be the case if the washing liquid were supplied to the machine in unrestricted quantities. The reason for this improved efiect appears to consist in the feature that the smaller liquid jets produced in this way and thrown by the blades of the impeller member against the articles to be washed during the partial filling of the machine have some kind of loosening efiect on the dirt. Further the motor l8 because of its typical construction rotates with the higher number of revolutions the smaller is the quantity of liquid in the machine. Fig. 4 presents a diagram of which the abscissa indicates the rate of liquid supply to the machine, for example by liters per second, and the ordinate indicates the washing eiiect. The figure shows a curve having a portion 88 paralleling or substantially paralleling the abscissa and a portion 89 steeply declining on both sides of a pronounced peak at 90. The portion 88 of the curve corresponds to the conditions existing if liquid is supplied to a dishwashing machine without any throttling means being provided, i. e. in the manner conventional before my invention. In one trial case a machine constructed in this manner was filled at a speed corresponding to the line 92 of the diagram. The rate being reduced, however, so much as to reach the branch 89, the washing effect was much improved so as to attain at the point 9%, as will be apparent from the diagram, its maximum Where it is perfect against any kind of dirt normally occurring on dishes with regard to the nature of food remainders adhering to the dishes as well as to the time of their drying before the washing operation normally is begun. The maximum effect is obtained with a considerable throttling as will be apparent from the curve line in question.

As an example of the eifect obtained when proceeding according to the invention I may mention one case in which the machine was capable of holding a maximum quantity of 3.5 liters of liquid. The throttling members being kept out of operation, a cleaning effect was obtained corresponding to the curve branch 88 independent of whether the machine was filled with liquid prior to the starting of the motor or this latter was started when the machine was still empty. The peak point 90 was reached by restricting the rate of supply of liquid to a value between one third and one fifth of the usual available rate of domestic water supply for machines of the kind under consideration.

While one more or less specific embodiment of my invention has been shown, it is to be understood that the same is for purpose of illustration only, and that my invention is not to be limited thereby, but its scope is to be determined by the appended claim.

What I claim is:

The method of operating a washing machine of the type having an upper receptacle for receiving articles to be washed, a lower trough in open communication with said receptacle, an open drain leading from said trough, an impeller located in said trough to rotate about a horizontal axis to throw washing water upwardly over said articles and to oppose flow of water from the trough into said drain and means for driving said impeller, which consists in admitting washing water to said trough after activating said impeller at such restricted rate that the level of water in the trough rises very slowly until the water level rises to a height at which the static head created causes drainage flow through the open drain at a rate equal to said restricted rate of admission to thereby maintain a substantially constant quantity of water in the machine and 10 thereafter continuing to admit water to and drain water from the machine at the established substantially equal rates until the desired Washing cycle is completed.

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Blakeslee Apr. 30, 1929 Snyder Dec. 5, 1933 Snyder et al. Dec. 17, 1935 Kempton Jan. 3, 1939 Ehret Aug. 27, 1940 Schulz July 11, 1944 Hollerith Dec. 27, 1949 

